Touch-sensor-integrated pens interact with a grid of capacitive-touch electrodes that exist below an electronic display. A touch-sensor-integrated pen can be further classified as a passive stylus or an active stylus (e.g., an active pen).
The passive stylus utilizes sensing methods based on changes in the capacitive coupling between sensor electrodes deposited on a touch-screen sensor and an input object, such as a rubber-tipped stylus or human figure. For example, electrical signals are driven on a set of conductive transparent electrodes deposited on one axis of the touch-screen sensor, while synchronized sensing of electrical signals takes place on a perpendicular set of electrodes. While a passive stylus can work well for human-touch detection, this solution may be less effective when fine tip pens are used. Also, challenges exist in distinguishing a passive stylus from fingernails and other fine user touches.
In contrast, active styluses drive unique modulated signals from the tip of the stylus to a grid of electrodes (e.g., a digitizer) and utilize sensing methods based on changes in the capacitive coupling between sensor electrodes. In these devices, sensing may take place on both axes simultaneously, with the received magnitudes being proportional to the tip proximity to the electrodes. Some active styluses may work in conjunction with a display that also supports touch-sensing. For example, the modulated content-rich signals of the active styluses may be received orthogonal to the touch-signals to facilitate differentiation between passive sensing and touch-sensing.